WASHINGTON, March 6 (Reuters) - The FBI is investigating 300 people who were admitted into the United States as refugees as part of 1,000 counterterrorism investigations involving Islamic State or individuals inspired by the militant group, congressional sources told Reuters on Monday, citing senior administration officials.

Department of Homeland Security officials did not provide details of the investigations or the current immigration status of those 300 individuals during a briefing with congressional staffers, according to the sources, who requested anonymity. (Reporting by Patricia Zengerle; Writing by Doina Chiacu; Editing by Chizu Nomiyama)